The present invention relates to an arrangement for detecting a force, which occurs between two oppositely movable machine parts, for monitoring especially cyclically repetitive production processes, for example by deformation or machining, whereby desired values determined and stored in a preliminary run are continuously compared with the actual values during the production. Furthermore, an apparatus is provided for carrying out the foregoing procedure, and finally a cold-solid deformation press or punch is provided which has at least one tool comprising a matrix and a punch; the tool additionally is provided with an ejector pin which can be actuated by an ejector lever and can be adjusted by an adjusting screw; the force absorbed by the tool is monitored pursuant to the present invention.
In a majority of cases, during production or manufacture of parts, it is necessary to produce the final shape of the parts by giving an appropriate shape to the blanks or intermediate products. With such a profiling for producing parts, features are preponderantly employed with which the profiling occurs by the application of force between a tool and the workpiece. The profiling can occur either by a deformation or forming of the workpiece to the tool shape, or by chip-removing according to which, proceeding from a blank, the excess material is removed with suitable tools until the finished contour is obtained. In both cases, forces arise between the tool and the workpiece, which forces affect the profiling.
For such profiling there is characteristic that correlations exist between the forces effective during the profiling and the produced design or configuration of the workpiece; these correlations make it possible to draw conclusions from the behavior of the process forces, especially as to whether the profiling procedure occurs orderly, i.e., in its entirety in the provided way and manner.
German Pat. No. 26 43 759 discloses a method for monitoring cyclically repetitive production processes; this method permits automatic monitoring of production machines with the aid of the process forces as monitoring parameters. This method has in the meantime proven itself in practice, and has found wide acceptance in the industry.
A prerequisite for using this method is that significant information is obtained from the respective production process for the process behavior. The quality of the production monitoring is that much better the more significant the information is therewith. Through a series of investigations, there was confirmed in the meantime that the most significant information for the production monitoring can be obtained from the aforementioned process forces, because here the clearest correlation exists between the behavior of the forces and the progress of the profiling procedure.
In order to be able to detect the forces occurring between the tool and the workpiece during production, it is known to detect the forces occurring between two oppositely movable machine parts by determining the effect or application of the respective force on an intermediate part located between the two machine parts. The force applications on this intermediate part are converted into electrical signals, so that only such electrical signals have to be evaluated. The conversion of the force applications into electrical signals is possible either according to the piezoelectrical measuring method or by the use of stress-measuring strips. During a piezoelectric measuring procedure, quartz discs are pressure-loaded, whereby the charges induced on the quartz surface during the pressure-loading of the quartz discs is directly proportional to the force transmission. During the conversion method using stress-measuring strips, these strips are applied to the force-biased part in such a way that they participate in the expansion or compression of this part. The expansions or compressions lead to a change of resistance of the wire loops provided in the expansion measuring strips, whereby force-proportional electrical signals are obtained.
For detection or determination of a force arising between two oppositely movable machine parts for monitoring production processes, it was previously customary to produce a special intermediate part which was inserted in the flux of force between the two oppositely movable machine parts, and which transferred the entire force between the two machine parts. German Pat. No 28 14 988, for example, discloses an apparatus for detecting a force occurring between two oppositely movable machine parts; with this apparatus, the intermediate part is loaded with the entire forces arising in a machine part, and to avoid an overloading in a separating plane provided for the intermediate part of the machine part, while forming a gap, this intermediate part is arranged in such a way that the gap is closed when a predetermined force is reached. The intermediate part, which is provided with force-measuring elements, for example stress-measuring strips, is protected against overloading in this manner.
For carrying out the known method for detecting a force arising between two oppositely movable machine parts, it was therefore necessary to change the structure of the respective machine which was to be monitored to the extent that intermediate parts provided with measuring elements had to be inserted in the flux of force of the machine. The entire process forces for the profiling procedure had to be transferred through these intermediate parts so long as the predetermined value of an overload was not exceeded thereby.
These known measures for carrying out the known monitoring method, however, are not only complicated and costly, but also prevent an expansion of the process monitoring in that:
in many machines no space is available for subsequent accommodation of force-measuring elements;
alteration of the machine construction is too costly with respect to the installation of force elements, so that a process monitoring can no longer be economically employed;
the operating range of the machine is restricted, for example by a shortening of the length of stroke of presses; and
the force-measuring elements can be arranged only so far from the central process phenomenon that no longer solely purely process forces are measured, but rather superimpositions occur with dynamic forces in the machine support and with other forces from driving elements of the remaining machine mechanism.
It is an object of the present invention, starting from the previously described state of the art, to provide a press apparatus for detecting or determinating a force which occurs between two oppositely movable machine parts for monitoring production processes. The press apparatus is to make it possible to detect significant stresses of the production processes, for example by deformation or machining, not only with newly produced machines, but also with production machines already being employed in the industry, so that for production monitoring, desired values determined and stored in a preliminary run can be continuously compared with the actual values during the production. The cost for originally equipping or supplementing for the inventive press apparatus associated therewith is to be reduced to a minimum, whereby the forces to be detected additionally are to be detected where the forces are procedurally significant to the greatest extent, preferably in the direct vicinity of the profiling region of the machine. The press according to the present invention, and the apparatus associated therewith, finally should be usable with widely differing profiling processes to avoid uneconomical design approaches for individual machines.